1 Overview
1.1 Introduction
The QT1106 is an easy to use sensor IC based on
Quantum’s patented charge-transfer (‘QT’) principles for
robust operation and ease of design. This device has many
advanced features which provide for reliable, trouble-free
operation over the life of the product. In particular the
QT1106 features advanced self-calibration, drift
compensation, and fast thermal tracking. Unlike prior
devices, the QT1106 can tolerate power supply fluctua tions
better in order to eliminate the need for a voltage regulator in
many cases.
1.3 User Interface Layout Options
The QT1106 can sense through all common plastics or glass
or other dielectric materials up to 10mm thick. It can be used
to implement a linear slider or rotary scroll wheel plus seven
additional discrete keys. The slider or wheel indicat es
absolute positions.
1.4 Slider and Wheel Construction
The QT1106 can connect to either a wheel or a linear slider
element (Figure 1.1). Selection of wheel or linear operation
is set through an SPI command. The basis of these designs
is found in US Patent 4,264,903 (expired).
The first and last positions of the linear slider have larger
touch areas.
As with touch button electrodes, wheels and sliders can be
constructed as etched areas on a PCB or flex circuit, or from
clear conductors such as Indium Tin Oxide (ITO) or screen-
printed Orgacon™ (Agfa) to allow backlighting effects, or for
use over an LCD display.
1.2 Burst Operation
The device operates in burst mode. Each key is acquired
using a burst of charge-transfer sensing pulses whose count
varies depending on the value of the sense capacitor Cs and
the load capacitance Cx (finger touch capacitance and circuit
stray capacitance).
The channels’ signals are acquired using three successive
bursts of pulses:
Burst 1: B1, B3, B5, B7 (for discrete keys 1, 3, 5, 7)
Burst 2: B2, B4, B6 (for discrete keys 2, 4, 6 )
Burst 3: A1, A2, A3 (for wheel or slider)
Bursts always operate in 1, 2, 3 sequence as a group and
occur one right after the other with minimum delay. The
groups are separated by an interval of time that can be used
for SPI communications.
Spread-spectrum operation
- Bursts can operate over a
spread of frequencies, so that external fields will have
minimal effect on key operation and emissions are very
weak.
Spread-spectrum operation works together with the ‘detect
integrator’ (DI) mechanism to dramatically reduce the
probability of false detection due to noise. An external RC
circuit is required to implement spread spectrum, but this
circuit is optional.
1.5 QMagic
TM
Proximity Effect
Channel 7 of the QT1106 can optionally operate a ‘magic on’
function based on hand or body proximity to a product. By
using a relatively large electrode inside the product’s
enclosure and a larger value of Csb7 (see Figure 2.1), the
product can auto power up or activate its display with hand
approach. This simple feature can add enormous sales
appeal to almost any product.
1.6 SPI Interface
The QT1106 uses a five-wire SPI interface. In addition to the
standard four SPI signals (/SS, SCLK, MOSI and MISO),
there is a DRDY (data ready) output for flow control.
The QT1106 also provides a CHANGE signal to indicate
when there has been a change in detection state. This
removes the need for the host to poll the QT1106
continuously.
On each SPI transfer the host sends three bytes to the
QT1106 and the QT1106 simultaneously sends three bytes
to the host. The bytes sent from the host provide the QT1106
with all its configuration information; the bytes sent from the
QT1106 convey the key states.
Figure 1.1 All-Metal Slider and Wheel Construction
(downloadable example CAD files for wheels and sliders can be found on the Quantum
website,http://www.qprox.com/toolbox/1106 )
Tips of triangles should be
spaced <=4mm apart.
SNSA3
SNSA1
SNSA2
SNSA3
<=4mm
<=4mm
Position 0
SNSA3
0
1 to 126
Position (at 7 bits - 0 to 127)
127
Position 85
SNSA2
Position 43
SNSA1
Lq
3
QT1106-ISG R8I.05/0906
QUANTUM [ QUANTUM RESEARCH GROUP ]
